Methods: The investigators used a single dose of the partial NMDAR agonist, d-cycloserine (DCS) to probe the effects of enhancing NMDAR signaling on working memory and plasticity. Working memory was assessed using a spatial n-back task. Plasticity was assessed using two learning tasks, the weather prediction task and information integration task, and an EEG paradigm that assesses changes in visual evoked potential amplitude following high frequency visual stimulation. Sixty-five healthy adults and forty-five schizophrenia patients were randomized to receive 100 mg acute DCS (healthy adult n = 32; schizophrenia n = 24) or placebo (healthy adult n = 33; schizophrenia n = 21).